In principle, a stabilizer, which operates according to the principle of the torsion bar, is arranged in parallel to the vehicle axle and is fastened to a wheel suspension at both ends, is assigned to each axle of a motor vehicle. This stabilizer substantially prevents or weakens the transmission of the rolling motions, which are caused by the road conditions and originate from the wheels to the vehicle. Such rolling motions occur especially in road curves or under rough road conditions.
The dimensions and the material properties of one-part stabilizers are designed for a predetermined spring rate, so that they can absorb torsional forces and generate corresponding opposing forces in a certain order of magnitude only. Therefore, the response of one-part stabilizers to different loads is either too weak or too hard, which has an unfavorable effect on driving smoothness. One-part stabilizers for motor vehicles, which are intended for use both on the road and off the road, are therefore suitable only conditionally. A split stabilizer, which comprises two stabilizer parts and in which the two are connected to one another via an actuator that increases the angle of rotation, is therefore used for such applications. Such an actuator may be, for example, a hydraulic oscillating motor, an elastic rotary coupling or a shiftable coupling.
Each of these actuators comprises, in principle, an outer rotary part, which is connected via a cover and a flange to one of the two stabilizer parts, and an inner rotary part, which is in connection with the other stabilizer part via a shaft. Both rotary parts of the actuator are designed such that they are rotatable over a limited angle. Conventional clamping or screw bushes are used, as a rule, as connecting parts between the flange and one of the stabilizer parts as well as between the shaft and the other stabilizer part.
Such split stabilizers meet the great variety of requirements. However, they have an essential drawback. Thus, each actuator is a compact unit with a considerable longitudinal extension, which is to a corresponding extent to the detriment of the effective springing lengths of the two stabilizer parts.
To improve the spring rate, s split stabilizer with an optimized spring rate is known from DE 100 12 915 A1, in which the outer rotary part of the actuator and one stabilizer part as well as the inner rotary part of the actuator and the other stabilizer part are each made in one piece. One stabilizer part is thus extended up into the radial plane of the force-generating rotary parts of the actuator, so that the two stabilizer parts are effectively interrupted only by a short axial distance from one another. This has functional advantages, but it can be manufactured with an increased effort only because of the length and the multiply curved shape of the stabilizer part as well as because of the necessary high accuracy of fit of the inner rotary part of the actuator.
A corresponding oscillating motor, whose inner rotary part has two axial and opposing blind holes, is known from U.S. Pat. No. 5,700,027. The two blind holes have different depths, the deeper blind hole being provided with an inner profile for connection to a correspondingly shaped first stabilizer part and the shorter blind hole being designed to receive a nonprofiled end of the second stabilizer part. The different lengths of the blind holes and the different shapes thereof shall prevent the two stabilizer parts from being transposed during assembly. The bottoms of the two blind holes are designed for this purpose as stops for the two stabilizer parts. The two blind holes are axially spaced from one another to the extent that a sufficient installation space is left for passing through connection channels for the pressure and suction chambers of the oscillating motor.
Even though the drawbacks in terms of manufacture compared to the one-part variant are eliminated with the two-part design and the profiled connection of the inner rotary part to one stabilizer part, an increase in the manufacturing effort for connecting the outer rotary part to the second stabilizer part must again be accepted at the same time due to the necessity of the second blind hole in the inner rotary part. In addition, the cost is increased by the fact that the force-transmitting profile in the blind hole can be shaped in a complicated manner only. It is also disadvantageous that the profiled connection between the inner rotary part and the corresponding stabilizer part is designed as a pure positive-locking connection. However, such a positive-locking connection is associated, in principle, with a clearance between the two components, which entails functional drawbacks and can be minimized by the manufacturing technology at an unacceptably great effort only.
However, a substantial drawback develops due to the fact that the profiled connection of the inner rotary part to the first stabilizer part is arranged outside the axial center of the axial length of the rotary wing, which the axial length is decisive for the generation of the force. This is due to the presence of the opposite blind hole and the radial pressure chamber connection channels. This eccentricity leads to a shortening of the effective spring length of the first stabilizer part and hence to a deterioration of the spring rate.